1. Anuario Estadistico Agropecuaria, 1978. Ministerio de Agricultura y Cria, Caracas, Venezuela.
2. Boletim estatistico, XXIV;Banco,1947
3. Fire, primitive agriculture, and grazing in the tropics;Bartlett,1956
4. Tropical savannas, a sequence of forest felling and repeated burnings;Budowski;Turrialba,1956